1. Field of the Invention
The present invention relates to a kneading segment, and kneading equipment, in which this kneading segment is employed.
2. Description of the Related Art
In general kneading equipment such as an extruding machine and a kneading machine, pellets of polymer resin serving as a base material, and powder additives are supplied into a barrel, the base material and additives are simultaneously kneaded and fed to the downstream side of the barrel by plural (in most cases, two as a pair) parallel kneading screws that are inserted in the barrel, thereby a composite resin material such as a plastic compound is manufactured.
A kneading segment is provided at a part of each kneading screw employed in kneading equipment, part which is located along the axial direction of the kneading screw. As such kneading segments, there are a rotor segment and a kneading disc segment. As shown in Japanese Patent Application Publication No. 2009-196303, for example, the kneading disc segment has plural wing portions along the axial direction.
Each wing portion of a kneading disc segment projects radially outward from a shaft center (projects from two positions 180° apart from each other in the circumferential direction), and has a substantially elliptical cross section (shape of an overall end surface including both ends on both sides), which is perpendicular to the axial direction. In addition, the wing portions are provided such that their angles, around the shaft, are different from each other (shifted by an increment of 90°, for example).
Kneading segments are arranged at the same positions, along the axial direction, of respective parallel kneading screws. Thus, when the kneading screws rotate, the wing portions of the kneading segments mesh with each other, whereby material is led to between a leading end of each wing portion and an inner wall of a barrel and to between meshing wing portions, and thus the material is kneaded.
In order to improve the degree of kneading, a gap between a leading end of one of meshing wing portions and a base end of the other wing portion (hereinafter referred to as “radial direction clearance”) is reduced by, for example, increasing the length of the wing portion leading end. Similarly, a gap between a wing surface of one of meshing wing portions and a wing surface of the other wing portion (hereinafter referred to as “axial direction clearance”) is reduced by, for example, increasing the thickness of the wing portions. These measures do not only improve the degree of kneading but also provides an action that material that adheres to parts forming the radial direction clearance or the axial direction clearance can scraped with the wing portions (action that kneading segment cleans itself) is also obtained.
As a type of screw used in an extruder or the like, a screw on an outer surface of which a film of diamond or the like is formed (for example, refer to Japanese Patent Application Publication No. H5-42569) is known. In order to improve the abrasion resistance, and the adherability of material, the film of diamond or the like is formed on the screw in this way.
The measure, which reduces the radial direction clearance and axial direction clearance between meshing wing portions, also deteriorates the flow condition of material that is located in the radial direction clearance. More specifically, a part of the material is made to stay between meshing wing portions. In the staying material, deterioration and chemical reaction progress with the elapse of time. Thus, the staying material becomes impurities having quality difference between themselves and normally kneaded material.
By any chance such material, which is impurities, is mixed with normally kneaded material, which leads to the deterioration of quality of extrusion extruded from kneading equipment (causes so-called contamination).
On the other hand, the screw used in extruders and the like, screw on an outer surface of which a film of diamond or the like is formed, loses its original actions of improving the abrasion resistance and the adherability of material, when the film peels off due to aging degradation or the like. More specifically, there is a fear that material adheres. Thus, degradation and chemical reaction progress in the material that adheres, and the material becomes impurities. Thus, this similarly leads to the deterioration of quality of extrusion.
In addition, if a film that peels off is mixed in material during the kneading, this leads to the deterioration of quality of extrusion extruded from kneading equipment.
In consideration of the above-mentioned situation, the present invention is made and has an object to provide a kneading segment and kneading equipment which do not generate material in which degradation and chemical reaction occurs with the elapse of time, i.e. impurities by preventing the material from staying between parallel kneading segments, and thus prevents impurities from being mixed into normally kneaded material, and thus can prevent the deterioration of quality of extrusion (can maintain high quality of extrusion).